The present invention is directed toward a dental bur and more particularly toward such a bur which is useful in the preparation of a tooth for restoration.
Dental burs of various sizes and shapes have been known and used for many years. The majority of these burs are comprised of axially extending steel bits which are coated on the working surfaces thereof with abrading material such as industrial diamond chips. An uncoated shank portion is held in a dental drill.
Burs of this type are often employed to remove enamel and dentin from a tooth in order to prepare the same for the placement of a restoration. Such restorations may be comprised of metal, plastic, quartz, porcelain or a variety of other materials or combinations thereof.
Occasionally a tooth is so broken down by decay or trauma that it must be reinforced by surrounding the entire tooth with the restoration material. The sides and chewing surfaces of the tooth are removed with the diamond burs so that there is space for the restoration or replacement. Restorations of this type are normally referred to as "crowns" since they replace the anatomical crown of the tooth with its size and shape duplicating the contours of the original enamel crown.
Crowns for front teeth are frequently made from tooth-colored material such as porcelain or porcelain-coated metal so as to look natural. As the sides of the tooth are being reduced in order to prepare the same for a crown, the tip of the diamond bur must be placed under the gum line. This is done for aesthetic purposes to ensure that the crown will end under the gum where no one can see it. In other words, the line of transition between drilled and undrilled tooth, known as the finish line, is placed subgingivally or under the gum line.
The subgingival distance at which a finish line should be placed is dependent upon the biological dictates and aesthetic requirements of the patient. Let us suppose, for example, that the dentist wishes to place the finish line 1 mm subgingivally. However, as the elongated bur is turning, there is no way to be certain how deep the bur has been placed subgingivally because known prior art burs are of a uniform color throughout the length of the working surface thereof. While Applicant is familiar only with burs having a uniform silver or black color, it is believed that burs have been proposed in the past having uniform colors other than silver or black.
Since a dentist has no way of being certain as to how deep the bur has been placed, the finish line may be uneven or ragged which can result in the improper fitting of a crown. To Applicant's knowledge, no one has ever proposed a dental bur which is particularly adapted to guide a dentist in the preparation of a subgingival finish line. In fact, Applicant is not aware of any previously proposed solution to this problem nor even the recognition of the same by others.